Chicago's controversial limits on e-cigarette usage took effect Tuesday, making it against city ordinance to use the devices within 15 feet of any entrance to public building.
The ordinance, passed in January, also puts restrictions on how e-cigs can be sold.
Health experts say those restrictions far outweigh the emotional reaction from proponents of e-cigarettes.
"Until more is known about just how dangerous those chemicals are in e-cigarette vapor, the most sensible solution is to keep our air clean," Joel Alfrick with the Respiratory Health Association said during a morning press event.
Beginning Tuesday, the use of e-cigarettes is prohibited in public places. Additionally, retailers must keep e-cigarettes behind the counter, just like regular cigarettes.
The Chicago Department of Public Health unveiled new signage that will replace the current "no smoking" signs seen around the city.
"This is mostly about protecting kids from picking up a deadly habit, and protecting the rights of our residents to breathe clean indoor air," said Chicago Health Director Dr. Bechara Choucair.
Critics of the ban maintain the devices have been an effective tool to ween smokers off real cigarettes.
The United States Centers for Disease Control and Prevention reported last September that use of the devices among middle and high school students doubled from 2011 to 2012. Eighty percent of those children who used e-cigs also said they smoked cigarettes, as well.
The Illinois General Assembly last year passed a bill that banned the sale of electronic cigarettes to minors. Gov. Pat Quinn signed that bill into law on Aug. 15, and it went into effect at the start of 2014.